1. Field of the Invention
The invention, in general, relates to a method of monitoring the rotational movement of a washing machine drum and, more particularly to a method of the kind referred to in a washing machine provided with a housing, a washing fluid tub mounted for oscillatory movement therein, a drum rotatably mounted therein for receiving laundry and/or washing fluid and a motor for rotating the drum in at least one direction as well as an evaluation device for preventing the continuation of a washing program upon detecting an impermissible movement during a first phase of the washing program during the which the motor is inactive.
2. The Prior Art.
Such a method is generally known from the disclosure of Patent Abstracts of Japan No. JP 2004065408A. It is provided with a sensor for detecting an impermissible movement of the drum or of the washing fluid tub during an idle time between initiation and execution of the washing program. A similar method has been disclosed by Patent Abstracts of Japan No. JP 10179978 A. A motion sensor or acceleration sensor mounted at an upper portion of the tub recognizes a detected movement as originating from a child within the drum. Its proper function is, however, dependent upon movements of the child.
Yet another method has been disclosed by German Laid-open Patent Specification No. DE 42 25 769 A1. In this case, weight present within the drum is detected by a weight sensor prior to initiation of a washing program and if the weight exceeds a predetermined threshold value the washing program is either not initiated or an alarm is activated. The method is suitable only for washing loads of no more than 4.5 or 5 kg of dry laundry, however. The method is unsuitable for larger washing machines with capacities of 8 kg of dry laundry because it cannot distinguish whether the detected weight originates with the permissible laundry in the drum or with a child of substantially the same weight.
European Patent Specification EP 0 709 512 B1 discloses a method of detecting the load within a drum. The number of rotations are monitored during reverse operation with a evaluation circuit determining the weight of the load as a function of the oscillatory behavior of the rotation signal.